In the 3D stereoscopic image display field in which a projected image is stereoscopically viewed as if the image is emerging and a powerful image may be enjoyed, recently, as 3D movies have been rapidly adopted by the general public, the 3D stereoscopic image display on a flat panel display, which is a closer scene, is beginning to draw great attention. In the related art, various modes in which images are stereoscopically viewed by naked eyes, or various modes in which dedicated glasses for watching stereoscopic images are used have been known in the stereoscopic display, but, unlike the case of sitting in a cinema and having an appreciation of a 3D movie, from the viewpoint that images may be seen in a situation of movement in daily life, the mode in which dedicated glasses are used draws attention.
In the meantime, the contents of 3D images for flat panel displays have not been sufficient yet. For this reason, there is a need for an image display mode in which conversion between 2D display and 3D display is capable of being easily implemented, and both the 2D images and 3D stereoscopic images may also be displayed with high quality. As a mode meeting these needs, two modes such as a shutter glasses mode (active glasses mode) and a polarizing glasses mode (passive glasses mode) draw particular attention. Further, in the flat panel display field in which high definition has recently progressed, it has been currently thought that it is impossible to provide a high-quality 3D stereoscopic image while maintaining a high definition on a flat panel display in the related art by any mode other than these two modes. Among them, improvement in the polarizing glasses mode is further required from the viewpoint that it is possible to be widely disseminated at a relatively low cost.
In the polarizing glasses mode, an image for the left eye and an image for the right eye are displayed on a display, image light for the left eye and image light for the right eye, which are emitted from the display, are made into two different polarization states (for example, right circularly polarized light and left circularly polarized light), respectively, and the display is observed through polarized glasses comprised of a polarizing plate transmitting right circularly polarized light and a polarizing plate transmitting left circularly polarized light, thereby obtaining a stereoscopic effect (see Patent Document 1). In addition, as a method for displaying an image for the left eye and an image for the right eye on a display in the polarizing glasses mode, a screen division mode for displaying half of an original image on each of the half of the display, has been adopted for the image for the left eye and the image for the right eye. As the screen division mode, a line-by-line mode has been widely adopted, and this is a mode displaying, on every odd number line and even number line of scanning lines (hereinafter, also referred to as lines) of the display, respectively, a half of an image for the left eye with the number of pixels reduced to half of the original image for the left eye which corresponds to alternate lines of the original image for the left eye and a half of an image for the right eye with the number of pixels reduced to half of the original image for the right eye which corresponds to alternate lines of the original image for the right eye. Furthermore, as a method for making image light for the left eye and image light for the right eye, which are emitted from the display, into two different polarization states, respectively, a method for attaching a pattern retardation film in which different retardations are patterned in a repeating belt-like shape and disposed in response to a line width on the display has been widely adopted.
Recently, for a pattern retardation film in which different retardations are patterned in a repeating belt-like shape and disposed in response to a line width of the image display device, improvement and reduction in manufacturing costs have been further required for dissemination of 3D image display devices.
Herein, as a manufacturing method of the pattern retardation film, various methods are known (see Patent Documents 1 to 5).
Patent Document 1 discloses a preparation method, including: using, as a material, a polarizing film stacked with an unstretched cellulose triacetate (hereinafter, also referred to as TAC) film which does not have birefringence and a stretched polyvinyl alcohol (hereinafter, also referred to as PVA) film having a retardation function, which is treated with iodine, coating a photoresist on the polarizing film, exposing specific regions of the PVA film having a retardation function, and then treating the regions with a potassium hydroxide solution to eliminate the retardation function of a part of the regions.
Patent Document 2 similarly discloses a preparation method, including: using, as a material, a polarizing film stacked with an unstretched TAC film which does not have birefringence and a stretched PVA film treated with iodine, providing a resist member on specific regions of the PVA side of the polarizing film, and then dipping the polarizing film in hot water to eliminate the retardation function of a part of the regions, and the like.
Patent Document 3 discloses a method for using two sheets of polymer films having a retardation of 140 nm as a material. As an embodiment in the same document, there is disclosed a method for manufacturing an optical film having two different birefringence regions derived from two sheets of polymer films on a substrate, including: stacking a polysulfone film on the substrate as a first sheet of a retardation film, providing a resist on a partial region of the polysulfone film, performing etching to form some parts of the pattern, covering the substrate and the patterned polysulfone film with a polystyrene film as a second sheet of a retardation film, disposing the first sheet and the second sheet of the retardation films such that the slow axes thereof are perpendicular to each other, providing a resist only on a portion covering the substrate, and performing etching. Further, in paragraph 0043 of the same document, it is described that other polycarbonate, polysulfone, polyarylate, polyethersulfone, polyether ether ketone and the like may be used as the polymer film.
Patent Document 4 discloses a preparation method in which the chemical etching treatment in Patent Document 3 is changed to a physically cutting treatment with a dicer. In addition, in paragraph 0079 of Patent Document 4, examples of the retardation film material include an H polarizing film composed of a film produced by containing iodine, a dichromatic coloring matter, a pigment and the like in an uniaxially stretched film, a K polarizing film such as a uniaxially stretched polyvinylene film, a film containing a dichromatic coloring matter and the like in a uniaxially oriented polymer liquid crystal film, and the like.
Patent Document 5 discloses a method for using, as a material, a retardation film containing a photochromic compound (photoisomerization material) having a photoisomerizable functional group) and a polymer which interacts with the compound. In an embodiment of the same document, with respect to a pre-treated sheet containing polyethylene terephthalate and a photoisomerization material, a photomask having a light transmission portion and a light non-transmission portion patterned into desired shapes is superimposed with a polarizing plate for obtaining a linearly polarized light to first irradiate ultraviolet ray having a wavelength corresponding to the photoisomerization material from the top side thereof at the first time, and a polymer of the retardation film in the portion through which the ultraviolet ray is transmitted is oriented in the transmitted axis direction of the polarizing plate. Next, the photomask is moved such that the light transmitting portion and the light non-transmitting portion are opposed to the previous time, the transmission axis of the polarizing plate is rotated at 90°, and then, ultraviolet ray is irradiated at the second time. The polymer of the retardation film with a portion through which the ultraviolet ray was not transmitted previously is oriented in the transmitted axis direction of the polarizing plate rotated at 90°, as compared to the previous time. Furthermore, in the same document, examples of the polymer used include polymers polycondensed with hydroxyl carboxylic acid, aromatic carboxylic acid, aromatic diol and the like, or poly(meth)acrylic acid copolymer, and also, it is described that a polymerizable resin may be included.